Welcome again, "The Untouchables", or EPOWER card that hold powerful VRM curcuitry for any overclocker needs.
There will be two versions, one is like on pictures below, 10 phase Volterra main unit + 3-phase auxilary unit.
Second version have smaller PCB and thus easier to use on low-end/middle-end videocards, and have only 8-phase Volterra unit.
Control, usage is exactly same principle for both devices. Voltage range for Volterra unit - 0.9 to 2.1V (default 1.2V), voltage range for 3-phase part - 1.2 to 4V (default 1.5V)

Take a note, pictures below show engineering sample VRM card, which have green PCB. Final retail units will have pearl black PCB mask.

Now take a look on videocards and find big beffy inductors of stock VRM curcuitry. To connect external power supply to card we need to disconnect onboard one first.
This can be easy done by desoldering original inductors. On 8600GT it's just single phase DC/DC's so one inductor per each VRM, one for memory, one for GPU.
On next photo I show already removed chockes. Big black one is from GPU VRM, smaller - from memory VRM.
You can clearly see that one side of choke go to VRM mosfets by big polygon (big solid copper area) and second go to output capacitors and furter go internal layers to GPU.
Our idea - to connect external power to this output capacitor polygon, thus having power flow into original power planes from external source.

STEP TWO

But first we need to find placement for EVGA "The Untouchables". Connections between VRM card and videocard must be as short as possible.
That's because of usual ohm law - higher resistance on line with high current flow cause voltage drop. So if we decrease resisance - voltage drop will be reduces.
With low-power GPU's like lowend and middle cards it's not that critical, but even now current between VRM and GPU can reach impressive 20-50 AMPs because of
relatively low voltage needed by GPU/memory. So find area where future VRM will be fixed, having in mind to keep path to onboard VGA power curcuitry shortest.

I decided to hook EPOWER on back of card. Why, you ask? Because front area will be covered by big cooler, but back one is free and have nice areas for soldering.
The only problem is card installed in motherboard, it must not block CPU cooler or other motherboard heatsinks in system. So check triple times before you solder VRM on!
I'm using F1 Gemini LN2 container on CPU, and did not spend enough time checking placement, so my assembled system will look very tight

Now important part. We found polygons of original VRM outputs, and now need to remove protective mask ink from PCB surface to have soldering access to copper.
You can use any tool suitable for scratching etc, I used my trusty Proxxon with sandpaper cylinder on it. Some shhrrr-shhrrr and job done as on picture.
Take care not to nake or short any other vias or traces on PCB, or you will need to repair broken connections. Also don't push too much force, coz copper layer is thin (35-70 micrometers often!)

After than check if card still ok, by measuring resistance on planes. Should not be shorted to <0.5 ohm resistance to ground. My 8600GT still ok, shows 2.88ish ohm on GPU
and 74.76 ohm on memory.

Remember these values, we should always check them before powering, to ensure there is no shorts somewhere.

Now we are ready to connect Untouchables to card itself. This will be done by short AWG12 wires. Solder wires on each plane, keeping symmetric connection to ground return too.
So if you soldered two wires for GPU power - solder two same wires to ground return. Current flow is not from one point to another, but is like endless flow by circle, from output to ground input.
Keeping shortest possible path for this current - is key to have lowest resistance value and reduce voltage drops.
General rule here - connect as much wires as possible, but keep in mind usability of final assembly.
Also solder joints must have enough solder to fix everything firm. Check shorts and solder balls on other components, avoid that.

Soldered now. From now better not to put force or stress on cards, because if you push too much - fragile polygons with heavy wires soldered on can be easily damaged.
On pic you can see two wires connected to each VRM section. Ground wires (4) are connected under The Untouchable.

Almost ready, time to add some extra capacitors.

And check some resistance. Should about same values we got on steps 5 and 6. If you have close to zero - somewhere you shorted power to ground. Remove short and redo measurement again.

Don't forget to check memory resistance too!

Now take cup of tea and relax, looking on abomination you created here. Now you can scary any normal human by showing what you have done with poor videocard.
Oh, I went some offtopic..

As for capacitors - use LowESR caps with suitable power rating (I usually use 2.5V for GPU and 6.3V for memory parts).
Connect them in right polarity to points on card, where you connected wires. Capacitors will help to smooth power drops under transients.
I always add some capacitance under GPU on back of PCB as well, on this point voltage drop is most critical, but also hard to reduce because of higher frequency.
So better use MLCC or good tantalum caps under GPU's, if you can fit them. Avoid long legs on caps or any kind of wires here, adding wires would not help anything.

You can also see that I added short ground wire for GPU VRM portion. Also usually good idea to add some bulk electrolytic cap on far end of memory power plane. You can easy
find points of memory power by checking resistance on surrounding MLCC ceramic capacitors.

Now check resistance of final zombie (tired , yea? ), and if everything ok -> mount your insane Kingpincooling container to GPU and assemble evil thingy to your system.
I will use 2600K and P67 FTW here. Don't forget to connect EVGA EVBot to port on "The Untouchables" EPOWER.

Now after everything booted and working ok - do your usual stuff, adjust voltages to desired levels, bring temperatures down, and perform your best on overclocking.
And take measurements of voltages directly on videocard, not on epower card. Because we have now noticeable voltage drop, so on this 8600GT lowend card setting 1.5V on EPOWER will get
1.42-1.45V on 3Dmark03, so to get real 1.5V you will need to set 1.55-1.57V on EPOWER. On heavy cards, like GTX 590 this got really serious, with 12+ wires connected between power card
and videocard there was big drop, what needed 1.7V on EPOWER to get 1.3-1.35V on load on GF110 GPU. So benefit is major from EPOWERs on lowend/middle-end cards, because
then don't eat as much current, so EPOWER will do best on cases where strong VRM limitation exist. Only EPOWER allowed me to overclock GTX590 to more than 1100MHz on GPU's, while all normal overclockers stopped on futile 800-900MHz at best.

I did not wasted time to try overclocking this card on stock VRM. You will be able to compare zombied card results with "regular" on hwbot after few days. I pretested it yesterday (with wrong OS, Win7x64 280xx drivers) and get ok with clocks. Tomorrow I will test with proper system setup and post scores if everything will be ok.

I will think about kit, but at first no, just "The Untouchables" card itself. Rest like wires, soldering iron etc should be easy to find, and coz this device targeted to extreme overclockers - they should already have everything

Max output current is 400 A for 10 phase, 320A for 8 phase and 60 A for 3-phase.